Tested the cubic interpolation now properly, also against alternative maths
This commit is contained in:
Weird Constructor
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@ -901,14 +901,14 @@ fn fclampc<F: Flt>(x: F, mi: f64, mx: f64) -> F {
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///```
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/// use hexodsp::dsp::helpers::cubic_interpolate;
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///
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/// let buf [f32; 9] = [1.0, 0.2, 0.4, 0.5, 0.7, 0.9, 1.0, 0.3, 0.3];
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/// let buf : [f32; 9] = [1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2];
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/// let pos = 3.3_f32;
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///
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/// let i = pos.floor();
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/// let i = pos.floor() as usize;
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/// let f = pos.fract();
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///
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/// let res = cubic_interpolate(&buf[..], buf.len(), i, f);
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/// assert_eq!((res - 0.4).abs() < 0.2);
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/// assert!((res - 0.67).abs() < 0.2_f32);
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///```
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#[inline]
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pub fn cubic_interpolate<F: Flt>(data: &[F], len: usize, index: usize, fract: F) -> F {
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@ -931,7 +931,31 @@ pub fn cubic_interpolate<F: Flt>(data: &[F], len: usize, index: usize, fract: F)
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let a = w + v + (x2 - x0) * f(0.5);
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let b_neg = w + a;
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(((a * fract) - b_neg) * fract + c) * fract + x0
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let res = (((a * fract) - b_neg) * fract + c) * fract + x0;
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// let rr2 =
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// x0 + f::<F>(0.5) * fract * (
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// x1 - xm1 + fract * (
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// f::<F>(4.0) * x1
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// + f::<F>(2.0) * xm1
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// - f::<F>(5.0) * x0
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// - x2
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// + fract * (f::<F>(3.0) * (x0 - x1) - xm1 + x2)));
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// eprintln!(
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// "index={} fract={:6.4} xm1={:6.4} x0={:6.4} x1={:6.4} x2={:6.4} = {:6.4} <> {:6.4}",
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// index, fract.to_f64().unwrap(), xm1.to_f64().unwrap(), x0.to_f64().unwrap(), x1.to_f64().unwrap(), x2.to_f64().unwrap(),
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// res.to_f64().unwrap(),
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// rr2.to_f64().unwrap()
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// );
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// eprintln!(
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// "index={} fract={:6.4} xm1={:6.4} x0={:6.4} x1={:6.4} x2={:6.4} = {:6.4}",
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// index, fract.to_f64().unwrap(), xm1.to_f64().unwrap(), x0.to_f64().unwrap(), x1.to_f64().unwrap(), x2.to_f64().unwrap(),
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// res.to_f64().unwrap(),
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// );
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res
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}
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#[derive(Debug, Clone, Default)]
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@ -1067,14 +1091,18 @@ impl<F: Flt> DelayBuffer<F> {
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let offs = s_offs.floor().to_usize().unwrap_or(0) % len;
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let fract = s_offs.fract();
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// (offs + 1) offset for compensating that self.wr points to the next
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// unwritten position.
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// Additional (offs + 1 + 1) offset for cubic_interpolate, which
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// interpolates into the past through the delay buffer.
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let i = (self.wr + len) - (offs + 2);
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let res = cubic_interpolate(data, len, i, f::<F>(1.0) - fract);
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// eprintln!(
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// "cubic at={} ({:6.4}) res={:6.4}",
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// i % len,
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// s_offs.to_f64().unwrap(),
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// res.to_f64().unwrap()
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// );
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// eprintln!(
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// "cubic at={} ({:6.4}) res={:6.4}",
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// i % len,
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// s_offs.to_f64().unwrap(),
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// res.to_f64().unwrap()
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// );
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res
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}
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@ -110,6 +110,51 @@ fn check_cubic_interpolate() {
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use crate::helpers::cubic_interpolate;
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let data = [1.0, 0.9, 0.8, 0.7, 0.6, 0.5, 0.4, 0.3, 0.2, 0.1, 0.0];
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let mut samples_out = vec![];
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let mut pos = 0.0_f32;
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let pos_inc = 0.5_f32;
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for _ in 0..30 {
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let i = pos.floor() as usize;
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let f = pos.fract();
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samples_out.push(cubic_interpolate(&data[..], data.len(), i, f));
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pos += pos_inc;
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}
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assert_vec_feq!(
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samples_out,
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vec![
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1.0,
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1.01875,
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0.9,
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0.85,
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0.8,
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0.75,
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0.7,
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0.65,
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0.6,
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0.55,
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0.5,
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0.45,
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0.4,
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0.35000002,
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0.3,
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0.25,
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0.2,
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0.15,
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0.1,
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-0.018750004,
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0.0,
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0.49999997,
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1.0,
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1.01875,
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0.9,
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0.85,
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0.8,
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0.75,
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0.7,
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0.65
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]
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);
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let mut samples_out = vec![];
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let mut pos = 0.0_f32;
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let pos_inc = 0.1_f32;
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@ -148,23 +193,7 @@ fn check_delaybuffer_cubic_interpolation() {
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let mut samples_out = vec![];
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let mut pos = 0.0;
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let pos_inc = 0.5;
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for _ in 0..20 {
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samples_out.push(buf.cubic_interpolate_at_s(pos));
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pos += pos_inc;
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}
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assert_vec_feq!(
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samples_out,
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vec![
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1.0, 0.95, 0.9, 0.85, 0.8, 0.75, 0.7, 0.65, 0.6, 0.55, 0.5, 0.45, 0.4, 0.35000002, 0.3,
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0.25, 0.2, 0.15, 0.1, 0.05
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]
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);
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let mut samples_out = vec![];
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let mut pos = 0.0;
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let pos_inc = 0.2;
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let pos_inc = 0.1;
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for _ in 0..30 {
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samples_out.push(buf.cubic_interpolate_at_s(pos));
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pos += pos_inc;
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@ -173,10 +202,54 @@ fn check_delaybuffer_cubic_interpolation() {
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assert_vec_feq!(
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samples_out,
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vec![
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1.0, 0.98, 0.96, 0.94, 0.91999996, 0.9, 0.88, 0.85999995, 0.84, 0.82, 0.8, 0.78, 0.76,
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0.73999995, 0.71999997, 0.6999999, 0.67999995, 0.65999997, 0.6399999, 0.61999995,
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0.59999996, 0.58, 0.56, 0.54, 0.52000004, 0.50000006, 0.48000008, 0.4600001,
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0.44000012, 0.42000014
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1.0, 1.03455, 1.0504, 1.05085, 1.0392, 1.01875, 0.99279994, 0.9646499, 0.9375999,
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0.91494995, 0.9, 0.89, 0.87999994, 0.86999995, 0.85999995, 0.84999996, 0.84, 0.83,
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0.82, 0.80999994, 0.8, 0.79, 0.78000003, 0.77000004, 0.76, 0.75, 0.74, 0.73, 0.72,
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0.71000004
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]
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);
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let mut samples_out = vec![];
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let mut pos = 0.0;
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let pos_inc = 0.5;
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for _ in 0..30 {
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samples_out.push(buf.cubic_interpolate_at_s(pos));
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pos += pos_inc;
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}
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assert_vec_feq!(
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samples_out,
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vec![
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1.0,
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1.01875,
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0.9,
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0.85,
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0.8,
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0.75,
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0.7,
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0.65,
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0.6,
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0.55,
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0.5,
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0.45,
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0.4,
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0.35000002,
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0.3,
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0.25,
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0.2,
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0.15,
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0.1,
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0.043750003,
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0.0,
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-0.00625,
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0.0,
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0.0,
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0.0,
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0.0,
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0.0,
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0.0,
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0.0,
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0.0
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]
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);
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}
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